I'm pretty sure this is an auto-Tweet because I've seen this happen before, but not with such tragic results.
Auto-Tweets from your blog or Facebook or wherever can be a huge time-saver. But that doesn't mean you should trust the app to make good contextual decisions for you. This is why we don't use the auto function.
But if you do, just remember to be very careful writing your tease. We advise clients to keep theirs to 100 characters or less (this also leaves room for easy RTs).